There's a correct way to use your chopsticks on a communal dish.

Turn them around so the end that touches the food is not the one you've been putting into your mouth all night.

Don't stick your chopsticks straight into your rice.

In China, it's tradition to stick burning incense into rice to honor the dead, so doing the same with your chopsticks is bad form.

Lift your cup with two hands when making a toast.

This tradition is more symbolic now than when it began centuries ago. Having your left hand on your cup in addition to your right would signify that you were unarmed. It's also seen as polite to grab a cup with two hands when it's handed to you.